Recently, there has been an increasing interest in energy storage technology. Electrochemical devices have been widely used as energy sources in the fields of cellular phones, camcorders, notebook computers, PCs and electric cars, resulting in intensive research and development into them.
In this regard, electrochemical devices are one of the subjects of great interest. Particularly, development of rechargeable secondary batteries has been the focus of attention. Recently, research and development of such batteries are focused on the designs of new electrodes and batteries to improve capacity density and specific energy.
Many secondary batteries are currently available. Among these, lithium secondary batteries developed in the early 1990's have drawn particular attention due to their advantages of higher operating voltages and much higher energy densities than conventional aqueous electrolyte-based batteries, for example, Ni-MH, Ni—Cd, and H2SO4—Pb batteries.
Such an electrochemical device generally comprises a cathode, an anode, and a separator interposed between the cathode and the anode. Each of the cathode and the anode comprises a current collector and an electrode active material layer formed by coating a slurry that contains an electrode active material, a polymer binder and a dispersing medium on the surface of the current collector, followed by drying.
Among electrode active materials, an anode active material may undergo volume expansion in the procedure that lithium is intercalated or disintercalated. In particular, a silicon oxide-based anode active material may result in more severe volume expansion.
Such a volume expansion of the anode active material may increase the size of pores formed on the surface of an anode active material layer, thereby generating cracks in an anode active material layer. From the generation of cracks, the anode active material may be released as cycles of electrochemical devices progress. From this, the charging and discharging characteristics and life characteristics of the electrochemical devices may be deteriorated.